Delaware · FIPS 10003 · County seat: Wilmington
New Castle County, DE GIS & Parcel Viewer
Looking for lot lines or a parcel number in New Castle County, DE? The quickest route is Delaware FirstMap State Parcels, the statewide parcel map we keep on file for this county. We link straight to it and add a few tips for getting around.
Open the New Castle County statewide map ↗
Opens delaware.maps.arcgis.com in a new tab. We link out and never embed or copy parcel data.
New Castle County at a glance
| Official map | Delaware FirstMap State Parcels |
|---|---|
| Type | Statewide map (covers all of Delaware) |
| Website | delaware.maps.arcgis.com |
| Access | Free, no login (checked Oct 2026) |
| County seat | Wilmington |
| Population | 578,592 (2023 Census Bureau estimate) |
| Land area | 426 sq mi |
| FIPS code | 10003 |
Who runs this map
This is a statewide map, not a county site. Delaware FirstMap State Parcels covers parcels across Delaware, and New Castle County is one part of it. A statewide layer can trail the county's own books by weeks or months, so treat it as a fast first look rather than the final word. As of our October 2026 test, anyone could open it without signing in or paying.
Searching for a parcel, step by step
- Open Delaware FirstMap State Parcels in a new tab and zoom to New Castle County (around Wilmington).
- Type a street address into the search box, or click directly on a parcel.
- Review the parcel attributes; field names vary by state.
- Confirm anything important with the county assessor, since the statewide layer is a compiled copy.
Many parcel sites expect owner names last name first. If a full name finds nothing, try just the surname.
The county in brief
Census Bureau figures put New Castle County at about 578,592 people (2023 estimate) on roughly 426 square miles of land, which is about 1,358 residents per square mile. That makes it the most populous of Delaware's 3 counties. Another 68 square miles of water fall within its lines, according to Census mapping. The county seat is Wilmington.
Neighboring counties
Parcels close to the edge of New Castle County can fall in the next county over. Neighboring counties:
- Kent County
- Cecil County, MD
- Chester County, PA
- Delaware County, PA
- Gloucester County, NJ
- Kent County, MD
- Salem County, NJ
A note on accuracy
The lines you see online are approximate. They're good for finding a lot and its parcel number, but a legal boundary question needs the recorded plat or a surveyor.